Coupling of electric waveguides



2, 1952 J. COLLARD ET AL. 2,606,967

COUPLING OF ELECTRIC WAVEGUIDES Filed Oct. 27, 1945 INVENTOR abfin Collard 2 fan/e 111']! ATTORNEY Patented Aug, 12, 1952 COUPLING OFYELECTRIC WAVEGUIDES John Collard, Hammersmith, London, and Stanley Hill, Staflrd,'England, assignors to Electric & Musical Industries Limited, Hayes, Middlesex, England, a-company of Great Britain Application October 27, 1945, Serial No. 625,086 In Great Britain May 18, 1944 1 Sectionl, Public Law 690, August s, 1946 Patent-expires May 18, 1964 1 v This invention relates to the coupling of electric radio frequency waveguides.

Usually, in order to couple sections of waveguide together, coupling elements are provided at the adjacent ends of the waveguide sections to be connected. Since it is diificult in practice to obtain perfect contact between the adjacent ends of the waveguide sections it has been sug-' gested, in order to prevent or reduce the escape of energy due to the imperfect contact between said adjacent ends, to provide the coupling ele; ments with surrounding flanges, the depth of the flanges being substantially equal to a quarter of the wavelength of the frequency of the energy transmitted through the guide so as to afford, in effect, a short circuit at the inner edges of the flanges. The adjacent surfaces of the flanges are usually flat and also serve for the reception of the bolts by means of which the coupling elements and the waveguide sections are securely held together. For the proper functioning of such an arrangement it is necessary for the flanges and the adjacent ends of the waveguide sections to be spaced apart by a short distance, and while it is possible to achieve this'result by the provision of an insulating washer between adjacent surfaces of the flanges, the use of washers is found to be an undesirable expedient in'practice. Consequently the flanges are usually bolted together so as to be in contact and, since it is diflicult to make a perfect contact between the flanges, the latter may contact only at points on the outer edges of the flanges which produces the reverse effect to that required.

The object, therefore, of the present invention is to provide an improved coupling for connecting adjacent sections of waveguide together in which contact between the flanges of the coupling can be obtained while, at the same time, the escape of energy at the coupling is substantially reduced or avoided.

In some kinds of waveguide, such as those of a rectangular cross-section and intended for the transmission of waves of the Hm mode or field configuration, it is known that when energy is transmitted through such guides, a longitudinal component of current flows along the longer sides of the guide but no longitudinal component of current flows along the shorter sides of the guide. The couplings according to the present invention, are intended-for use with such kinds of waveguide and the flanges of the coupling elements are arranged to contact only in the vicinity of the surfaces of the guide where no longitudinal component of current flows, and are e 8 Claims. (01. 178-44) 1 2 spaced apart in the vicinity of the surfaces. of the guide where a longitudinal current flows so that the flanges can function to quired effective short circuit.

' According therefore to the present invention, a coupling is'provided for sections of a waveguide, the waveguide being of the kind in which a longitudinal component of current flows :only along certain portions of the surface of the guide and not along other portions or. said surface, said coupling comprising-a pair of flanged coupling elements which are arranged to be in electrical contact adjacent the portions of the guide where no longitudinal component of current flows, and out of contact with one another adjacent the said portions Where a longitudinal flow of current occurs, thewidth. of the flanges adjacent to the latter portions of the guide beingsuch as to afford .an effective, short circuit at; the inner edges of said flanges.

Thus, by. virtue of the invention, it is possible to secure the. flanges directly together without the aid of interposedinsulating washers, and sincethe flanges-are out of contact adjacent the portionsof the-guide where a longitudinal component. of current flows, the flanges can function in the desired manner to afford an effective short circuit. Since the flanges only contact with one another adjacent those portions of the guide where no longitudinal component of current flows, it is immaterial whether good contact is madebetween such contacting surfaces of the flanges. Y

In order that the said invention may be clearly understood and readily carried into effect", it will now .be more fully described with reference to the accompanying drawing.

Figure 1 illustrates a side elevation of two sections of waveguide withcoupling means inaccordance with the invention, v

Figure 2 is a plan view of Figure 1,

Figure 3 is an elevationtaken along the line IIIIII of Figure 1, V

Figure 4 is a sectional elevation taken on lines IV--IV of Figure 2,, looking towards the righthand end of the arrangement shown in Figure 1,

Figure 5 is a plan view of two sections of Waveguide with coupling means in accordance with another form of the invention, and I Figure 6 is an elevation taken along the line VI-VI of Figure 5 and looking in the direction of the arrows.

Referring first to Figures 1 .to 4 of the drawing the reference numerals 6 and 1 indicate two sections of a hollow rectangular waveguide intended provide the refor the transmission of waves of the H mode. The adjacent ends of the sections 6 and l are provided with flanged coupling elements 8 and 9 to which the ends of the sections 6 and 1 are soldered, brazed or otherwise connected. In the form of guide shown in Figures 1 to 4, a longitudinal component of current flows along the longer sides (broad walls) of the guide while no longtiudinal component of current flows along the shorter sides (narrow walls) of the guide. The adjacent faces of the coupling elements 8 and 9 are arranged to contact with one another adjacent the shorter sides of the guide and are arranged to be out of contact with one-another adjacent the longer sides of the guide. For this purpose, as will be observed in Figures 1 and 2, bosses l and H are provided on the flanges adjacent the shorter sides of the guide sections, these bosses serving to maintain the rest of the area of the flanges out or contact and provides an air gap between the flanges. The coupling elements 8 and 9 are bolted together by the provision of bolts I2 and 13, these bolts passing through the flangesat the shorter sides of the guide sections. The width of the flanges of the couplingelements 8 and 9 where they are maintained out of contact is made effectively equal to a quarter of the free space wavelength of the energy transmitted through the guide so that an effective short circuit is provided at the inner edges of the flanges adjacent the longer sides of the guide. s

The dimensions of the bosses Hi and I I are such as to maintain the parts of the flanges adjacent the longer sides of theguide separated by as small an amount as possible. A separation of four th'ousandths of an inch is found suitable in practice. It will, of course, be appreciated that it is not necessary for each of the coupling elements to be provided with bosses since in some cases oneof the coupling elements may be flat and the other coupling element provided with bosses to afford the required separation.

Figures 5 and 6 of the drawing illustrates a modified form of the invention in which the face of one coupling element 8 is flat .while the other face of the coupling element 9 is provided with bosses M and 15. These bosses M and i5 instead of terminating adjacent the longer sides of the guide as do the bosses l0 and H of Figures 1 to 3, extend beyond the longer sides, assho'wn in Figure 5, and terminate at the longer sides of the coupling element 9. In this case, the width of the flanges where they are out of contact with one another is a quarter of the wavelength of the waves in the guide. If desired, both of the coupling elements may be provided with bosses. In an alternative construction both faces of the flanges may be flat and the required separation may be obtained by separate'interposed conduct ing spacing elements. It'is possible that the periphery of the flanges should not be straight as indicated in the drawing, but if the spacing between the flanges where they are out of contact is maintained small the exact shape or the periphery of the flanges maybe immaterial.

Although the invention has been described above as applied to waveguides of rectangular cross-section, it will be understood that the invention is not limited thereto since it can be applied to guides of other cross-sectionin which a longitudinal component of current only flows along certain portions of the guide.

What is claimed is:

1. A radio frequency rectangular waveguide coupling means comprising a pair of flanged coupling elements, each one of said flanged coupling elements being electrically secured to adjacent ends of the waveguide sections to be coupled by said coupling elements, at least one of said flanged coupling elements being provided with an integral boss to provide an air gap for maintaining said coupling elements out of contact with one another adjacent a portion where a longitudinal flow of current occurs, the width of said flanges at the out of contact portions being equal to an odd multiple including unity of one-quarter of a wavelength at the operating frequency, and to maintain the narrow walls of said sections in physical and electrical contact.

2. A coupling for a section of a waveguide, the waveguide being rectangular in form and excited in a mode at the operating frequency in which a longitudinal component of current flows only along certain portions of the surface of the guide and not along other portions of said surfacasaid coupling comprising a pair of flanged coupling elements which are arranged to be in electrical contact adjacent the portions of the guide where no longitudinal component of current flows and out of contact with one another adjacent the said portions where a longitudinal flow of current occurs, the flanges adjacent the latter portions of said waveguide being separated by an air gap and the width of said last flanges being such as to afford an effective short circuit at the inner edges of said flanges, and securing means passing through the portion of the coupling elements which are in electrical contact.

3. A separable coupling for two sections of hollow pipe waveguide each having a longitudinal axis and each defined by metallic walls and proportioned to be excited at the operating frequency in a mode in which a longitudinal component of current flows along first portions less than the whole of the transverse periphery of the inner surface of said walls and no component of lon tudinal current flows along other portions of the transverse periphery; comprising a pair of 'coupling elements having flanges separably to hold said sections with said axes in a continuous line and with said inner walls of each section'in contact with and smoothly joined to each other adjacent said other .portions thereof where said longitudinal currents do not flow, and to'hbld said sections with said walls at said first portions out of contact and spaced from each other, said flanges having closely spaced dielectrically sepa rated metallic surfaces facing each other for a transverse distance of and terminating eifective- 1y at an odd number of quarter wavelengths at said operating frequency from said first portion inn-er wall surfaces.

4. The coupling claimed in claim 3, at least one of said flanges including bosses to space said flanges. r

A separable coupling fortwo sections of hollow pipe rectangular waveguide each having a longitudinal axis and each defined bya pair of parallel broad walls and a pair of parallel-narrow walls, andproportioned to be excited at the operating frequency in the dominant mode in which a longitudinal component or current flows along said broad walls and not along the central part {of said narrow walls, comprising a pair of coupling elements having flanges separably to hold said sections with said axes ina continuous line and with said innerwalls of each section in contact with and smoothly joined to each other in those portions of said flanges adjacent the.

Wall portions in contact with each other.

8. The coupling claimed in claim 5, further comprising securing means comprising bolts inserted in said flanges adjacent said narrow walls.

JOHN COLLARD. STANLEY HILL.

6 REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS Number Name Date 2,155,509 Schelkunoff Apr. 24, 1939 2,360,660 Eaton Oct. 17, 1944 2,396,044! Fox Mar. 5, 1946 2,400,777 Okress May 21, 1946 2,402,540 Espley June 25, 1946 2,403,289 Korman July 2, 1946 2,434,115 McArthur Jan. 6, 1948 2,476,621 Okress July 19, 1949 FOREIGN PATENTS Number Country Date 517,209 Great Britain Jan; 23, 1940 

